1. Field of the Invention
The present invention is directed to a method for controlling successive machine processes, wherein at least first and second decentralized process control units for different machine processes are connected to one another and to a central control unit.
2. Description of the Prior Art
Such successive machine processes play a part, for example, in the automatic equipping of substrates (such as printed circuit boards or ceramic substrates) with components such as SMD (surface mounted device) components or BGA (ball-grid arrays). The individual components are taken from a magazine or a delivery device with an equipping head and are then positioned in a predetermined position on the substrate.
In this process execution, a large number (approximately 20-30 per component) of successive machine processes are implemented, many of these only being allowed to be implemented if the machine process sequencing earlier in time was successfully completed. Such process sequences also occur in further automatic processing units required in the equipping process such as, for example, for applying glue points onto substrates. For monitoring this compulsory sequence of the machine processes, the individual control units that control and monitor the individual decentralized machine processes are connected to a central control unit that monitors the entire process execution. Each individual control unit communicates the end of the machine process which it controls to it to the central control unit, and the central control unit subsequently communicates a start command to the control unit responsible for the following machine process. Since, however, the central control unit controls a number of machine processes sequencing in parallel, and sequences additional tasks such as, for example, communication with an operator of the automatic equipping unit, time delays between the reception of the end signal from a first decentralized control unit and the output of the start command to a second decentralized control unit occur. Given a large number of successive machine processes, considerable losses of time, and thus equipping performances that are too low, arise. In addition, the communication between the decentralized control units and the central control unit occupies takes time that reduces the equipping performance.
One possibility for shortening the time would be to provide different central control units for different tasks, for example one central control unit controls tasks an additional central control unit for communication between the operator and the machine and for data editing. Communication among the various central control units, as would be necessary in such an approach, however, would still require an undesirable time expenditure.